Nowadays, the friction material used in vehicles contains a great of heavy metal comprising copper, chromium, cadmium, lead, and the like. A small amount of heavy metal dust may be released from vehicles during every time of braking, which can be accumulated to be harmful in the environment. For example, the compound of cadmium can be absorbed in vivo through breathing and be accumulated in liver or kidney, hereby do harm to kidney and liver. Copper-containing dusts may become biological toxicants for fishes such as salmons after entering into the environment. It is shown that 30% percent of the copper pollution in the environment is caused by brake pad of vehicles. Therefore, the influence of the brake pad of vehicles on the environment must be focused on. Currently, the whole world is making research in how to prevent such phenomenon proceeding. For example, No. SB6577 Bill was signed by the governor of Washington state of US, Chris Gregoire and was allowed in the 61st legislative session. The Bill intends to gradually forbid the use of copper in brake pad of vehicles, and will severely punish transgressors, which cites: since Jan. 1, 2014, the friction material for flake pad of vehicles sold in or to Washington by manufacturers, retailers and dealers shall contain the following substances without exceeding the limited amount based on the total weight: 1. asbestos fibers, no more than 1%; 2. cadmium and the compounds thereof, no more than 0.01%; 3. chromium salts, no more than 0.1%; 4. lead and the compounds thereof, no more than 0.1%; 5. mercury and the compounds thereof, no more than 0.1%. Since Jan. 1, 2021, the friction material for flake pad of vehicles sold in or to Washington by manufacturers, retailers and dealers shall contain no more than 5% of the total weight of copper. Meanwhile, an advisory committee of experts in industry, safety and environment was established to research and assess the feasibility of limiting the amount of copper within 0.5% in the future.
Coincidentally, also in 2010, Schwarzenegger, the governor of California state signed and allowed No. SB346 Bill to require all the manufacturers of brake pad of vehicles to reduce the amount of copper in the friction material of brake pad sold in California state, to no more than 5% till 2021, and to no more than 0.5% till 2025.
The above two American bills indicate the requirement of human for environment protection more severe and careful. Therefore, the manufacturers of parts for vehicles have to draw attention to this, and under the provision that the characteristic of brake pad is assured, it is necessary to find safer, more effective and environmentally friendly friction material to replace heavy metals such as copper so as to meet with the gradually severe requirement for environment protection.